Cyanean Rocks

(The). The Symplegades at the entrance of the Euxine Sea. Said
to close together when a vessel attempted to sail between them, and
thus crush it to pieces. Cyanean means dark, and Symplegades
means dashers together.

“Here are those hard rocks of trap, of a greenish-blue,coloured with
copper, and hence called the Cyanean.” —Olivier